Known is a method for curvilinear folded structure production at geometrical conjunction of the article and the transformable dies wherewith the article is shaped. It includes, at the first stage, placing of sheet blank onto the lower shaping transformable die whereas the similar upper transformable die is placed onto the blank. Equidistantly placed the upper and the lower transformable dies consist of plane shaping elements made in the form of parallelograms; the shaping elements are connected to each other along all the sides with the use of hinges.
At the second stage, when transforming the dies, e.g. with the use of vacuum bag, the upper and the lower transformable dies embedding into the blank change the curvature whereas the blank is put into relief form with crimp design parameters given (V. I. Khaliulin, Technological schemes for sandwich structures production, KSTU, Kazan, 1999.—168 p., p. 128-133.—ISBN 5-7579-0295-7).
The main short-coming of herein-presented method for sheet blank corrugation whereat the curvilinear article is attained is that with the aim to provide the given folded structure curvature defined with the use of mathematical computation are the distance between the upper and the lower transformable dies, the curvature radius required for imparting to the blank before shaping, and the dimensions of transformable dies shaping elements ridges. In addition, geometrical dimensions of the upper and the lower dies have different linear parameters. It results in labor-consuming mutual placement of dies at the first stage of shaping. It is impossible to attain the calculated value of the article curvature at failure to execute the strict geometrical conjunction of the upper and the lower shaping dies.
Known is a method for production of curvilinear corrugated core including the marking-out of protrusions and recesses zigzag lines on the blank development whereat the angles of vertexes are accordingly equal to 2α and 2β whose values are related to definite zigzag corrugated core design parameters, and further bending of blank along the marked-out lines (Inventor's certificate No. 1,785,154 USSR, Int. C1. B 32 B 15/00, Method for production of curvilinear sandwich panel with zigzag corrugated core, Bulletin No. 42 of Nov. 16, 1992). The given method is taken as a prototype.
The main short-coming of herein-presented method is that it is possible to produce folded structures only with longitudinal direction of zigzag crimps, e.g. in direction of cylinder generatrix. Yet, in production, e.g. of aircraft fuselage panels, it is necessary that the core should have lateral direction of crimps and should meet the use requirements for condensate removal from panels inner cavities.